JP2755593B2 - Information recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention causes a recording layer to change its optical characteristics due to a change in atomic arrangement by irradiating a light beam to record information,
The present invention relates to an information recording medium on which information is reproduced by repeatedly performing erasure and detecting a change in the optical characteristics.

(Prior Art) As an information recording medium capable of repeating information recording and erasing, a medium utilizing a phase change due to light beam irradiation has been developed.

When recording information on such an information recording medium, first, a light beam is applied to the entire surface of the recording medium to bring the recording layer into a state of high crystallinity (hereinafter referred to as a crystalline state). Next, in order to record information, the recording layer is irradiated with a short intense pulsed light and heated and rapidly cooled to bring the recording layer into a state in which the atomic arrangement is disturbed (hereinafter, referred to as an amorphous state). When erasing the recorded information, the recording layer is irradiated with a long weak pulse light, heated and gradually cooled to return from the amorphous state to the crystalline state again. In such a crystalline state and an amorphous state, optical characteristics such as reflectivity and transmittance change in accordance with a change in the atomic arrangement. By detecting the change in the optical characteristics, recorded information can be obtained. Playing.

As an information recording medium utilizing such a phase change,
JP-A-60-179952, JP-A-60-179953, JP-A-61-680
No. 6 publication. In these publications, Au _x Te _100-x , Ag _x Te _100-x (10 ≦ x ≦ 40 atomic%) and the like are proposed as the composition of the recording layer. However, with these materials, the stability of the recording state can be obtained, but the energy required for recording is large, so that there remains a problem in the recording and erasing characteristics.

(Problems to be solved by the invention) As described in detail above, the conventional Au _x Te _100-x and Ag _x Te _100-x (1
The information recording medium using (0 ≦ x ≦ 40) as a material has a disadvantage that the crystallization speed is low and the erasing characteristics are poor.

SUMMARY OF THE INVENTION It is an object of the present invention to eliminate the above drawbacks and to provide an information recording medium having excellent recording and erasing characteristics.

[Structure of the Invention] (Means and Action for Solving the Problems) In the information recording medium of the present invention, the average composition of the recording layer is (Ge _x Sb _100-x ) aChbMc, where Ch is Se, Te, or S. The selected chalcogen element M is a metal selected from Pd and Au. 50 atomic% ≦ a <100 atomic% 0 atomic% ≦ b <50 atomic% 0 atomic% ≦ c <30 atomic% 10 atomic% ≦ x < It is characterized by being 80 atomic%.

Among the constituent components, the alloy composed of Ge and Sb absorbs pulsed light, easily changes from amorphous to crystalline, and has a very large change in optical properties (reflectance and transmittance). . At this time, the composition range of Ge is preferably in the range of 10 at% to 80 at%, and in other ranges, a sufficient optical change amount cannot be obtained. That is, in order to obtain a high change in reflectance between crystalline and amorphous, the composition needs to be within this range.

The alloy composed of Ge and Sb is a main component in the recording layer that causes a change in the atomic arrangement. To cause this change, it is desirable that the alloy be contained in an amount of 50 atomic% or more. In other words, if the content of the elements represented by Ch and M below is 50 atomic% or more, it will hinder the optical change of the Ge Sb alloy.

The chalcogen element of Se, Te, S represented by Ch is Ge Sb
An amorphous state can be stably maintained by alloying with an alloy consisting of

Further, elements such as Pd and Au represented by M have effects such as an increase in crystallization rate and an improvement in sensitivity.

A sectional view showing the structure of the information recording medium used in the present invention is as shown in FIG.

The information recording medium of the present invention includes a substrate 12, a recording layer 13, and an organic protective layer 14. The substrate 12 is made of glass or a plastic material (for example, polymethyl methacrylate resin or polycarbonate resin). On this substrate 12, a recording layer 13 that undergoes a layer change by light beam irradiation is formed. The average composition of the recording layer 13 is (Ge _x Sb _100-x ) aChbMc, where Ch is a chalcogen element selected from Se, Te and S, M is a metal selected from Pd and Au, and A, b, and c are in the range of 50 atomic% ≦ a <100 atomic%, 0 atomic% ≦ b <50 atomic%, 0 atomic% ≦ c <30 atomic%, and 10 atomic% ≦ x <80 atomic% is there. Further, an organic protective layer 14 made of an ultraviolet curable resin or the like is formed on the recording layer 13.
Are formed.

Further, the information recording medium used in the present invention may have a structure as shown in FIG. 2 and FIG. The information recording medium shown in FIG. 2 has a structure in which an inorganic protective layer 15 made of metal, metalloid oxide, fluoride, sulfide, nitride or the like sandwiches the recording layer 13 in order to prevent the recording layer 13 from changing over time. It has become. The information recording medium shown in FIG. 3 has a structure having a composite layer 16 in which the material for forming the recording layer 13 is dispersed in the material for forming the inorganic protective layer 15.

Next, a method for manufacturing an information recording medium will be described with reference to FIGS. FIG. 4 is a side view of the film forming apparatus used in the present invention, and FIG. 5 is a bottom view of the film forming apparatus shown in FIG.

The film forming apparatus includes a vacuum vessel 17, an exhaust port 18, and an exhaust device.
19, gas introduction port 20, argon gas cylinder 21, support device 2
2, sputter sources 24a, 24b, 24c and motor devices 26a, 26b, 26c
It is composed of The vacuum vessel 17 is connected to an exhaust device 19 via a discharge port 18, and is connected to an argon gas cylinder 21 via a gas introduction port 20.
A support device 22 is provided in the upper portion of the vacuum vessel 17, and the substrate 12 is horizontally supported on the support device. The substrate 12 can rotate around the support device 22 as an axis. In addition, vacuum vessel 17
On the bottom, sputter sources 24a, 24b, 24c facing the substrate 12
, And a high-frequency power supply is connected to these sputtering sources. Further, monitor devices 26a, 26b, 26c are installed above the sputter sources 24a, 24b, 24c.

When forming a recording layer on the substrate 12 using this apparatus, first, the air in the container is exhausted by the exhaust device 19, and then the argon gas is introduced from the argon gas cylinder 21 to bring the inside of the container to a predetermined pressure. Hold. Then, while rotating the substrate 12, power is applied to the sputtering sources 24a, 24b, 24c for a predetermined time. The monitoring devices 26a, 26b, and 26c each monitor a sputter source of an element from the sputter source, and adjust power supplied to each sputter source so that the monitored amount becomes a predetermined value. Thus, a recording layer is formed on the substrate 12.

(Example)-Experiment 1-In this experiment, a recording film was formed by a multiple simultaneous sputtering method.

A desired sputtering source of Ge ₅₅ Sb ₄₅ , Te and Cr was provided in a vacuum vessel, and the inside of the vessel was evacuated to 8 × 10 ⁻⁶ Torr. Next, Ar gas was introduced to adjust the entire pressure to 4 × 10 ⁻³ Torr. A disc-shaped carbonate substrate with a 130 mm outer diameter and 1.2 mm thickness, which has been sufficiently cleaned, is used as a substrate. The amount of each element sputtered is monitored by monitoring the amount of each element sputtered by rotating this substrate at 60 rpm, and the power supplied to each sputter source is suppressed. Then, each element was deposited until the total film thickness became 1000 Angstrom to form a recording layer.

Further, an ultraviolet curable resin was overcoated as an organic protective layer on the recording layer by a spin coater of about 10 μm, and cured by irradiating ultraviolet rays to form an information recording medium having a desired composition.

-Experiment 2- Here, a change in the atomic arrangement due to light beam irradiation of the recording film was confirmed.

In Experiment 1, a sample having a recording layer composition of (Ge ₅₅ Sb ₄₅ ) ₈₅ Te ₁₀ Au ₅ was formed using Ge ₅₅ Sb ₄₅ , Te and Au as a sputtering source (unirradiated portion). When this sample was irradiated with pulse light of 5 mW and 10 μS focused on a beam diameter of 1 μm, the reflectance of the irradiated portion changed (unrecorded portion). Next, it was confirmed that the reflectivity of the irradiated part returned to its original state when a pulse light of 15 mW and 100 ns was applied several times (recording part). Next, in order to compare the crystal states of the unrecorded portion and the recorded portion, a diffraction pattern was observed using a transmission electron microscope. When the protective layer was peeled off from the sample and the state of the recording layer was observed from the diffraction pattern, a halo pattern peculiar to amorphous was observed in the portion not irradiated with the laser beam. Further, a diffraction ring and a spot showing a crystal structure were observed in an unrecorded portion of the laser light irradiated portion, and a halo pattern peculiar to an amorphous material close to the unirradiated portion was observed in the recorded portion. Similar changes in reflectivity and diffraction pattern were observed for recording curtains of other compositions.

-Experiment 3-In this experiment, the erasing characteristics of the recording section were evaluated. Samples were prepared in which the recording layer composition was (Ge ₅₀ Sb ₅₀ ) ₇₀ Te ₃₀ and Au was added to Te at a ratio of 5, 10, and 20 atomic% to Te.

The recording layer was crystallized by applying a pulse of 5 mW and 5 μS to the sample until the reflectance became constant. FIG. 6 plots the number of pulsed light irradiations until the reflectance becomes constant with respect to the added amount of Au. It was confirmed that as the amount of Au added increased, the change occurred even when the number of irradiations was small. That is, it was confirmed that the addition of Au can increase the crystallization speed and improve the sensitivity.

Further, the same effect can be obtained even when Pd is added instead of Au.

-Experiment 4- In this experiment, a test was performed using a practical test device. FIG. 7 is a schematic diagram of an apparatus used for the test. This test apparatus includes a spindle motor 32, a semiconductor laser source 34, a collimator lens 35, a beam splitter 36, a λ / 4 plate 37, an objective lens 38, a detection lens 39, a light receiver 40, a drive coil 41, a servo system
42.

The sample 31 is fixed on a spindle motor 32 and can rotate.

The light emitted from the semiconductor laser source 34 is a collimator lens 35
And becomes parallel light. Then the light is a beam splitter
Pass through 36, pass through λ / 4 plate 37, sample by objective lens 38
It is focused on 31. The light reflected from the sample 31 is the objective lens
After passing through 38 and the λ / 4 plate 37, it is reflected by the beam splitter 36. The reflected light is collected by the detection lens 39, enters the light receiver 40, and becomes a detection signal. Further, the detection signal is converted into a current through the servo system 42, and the drive coil 41
Then, the objective lens is driven by this current, and is accurately focused on a groove (guide groove) on the sample 31 on which information is recorded.

Using the method shown in Experiment 1, a medium sample in which both sides of the recording layer were sandwiched by SiO ₂ (thickness: 1000 Angstrom) was prepared and mounted on the above-described apparatus, and an experiment was performed. The recording layer composition is (Ge ₅₀ Sb ₅₀ )
_{At 70} Te ₃₀ , Pd was added to Te at 5, 11, 18 atomic%.
This sample was fixed on a spindle motor and rotated at 900 rpm.

Further, a pulse light of 5 mW and 15 μS was irradiated from above, and the amount of change in reflectance was measured. FIG. 8 plots the value (contrast ratio) obtained by dividing the amount of change by the initial value and the amount of Pd added.
It can be seen that the addition of Pd increases the contrast ratio. Further, the same effect can be obtained when Au is added instead of Pd.

[Effects of the Invention] As described in detail above, according to the present invention, it is possible to provide an information recording medium having good recording and erasing characteristics and being sufficiently practical.

[Brief description of the drawings]

1 to 3 are sectional views showing the layer structure of an information recording medium used in the present invention, FIG. 4 is a side view of a film forming apparatus, and FIG.
The figure is a bottom view of the film forming apparatus, FIG. 6 is a graph showing the amount of added Au and the number of irradiations, FIG. 7 is a schematic diagram of a practical recording apparatus, and FIG. 8 is a graph showing the amount of added Pd and the contrast ratio. . 12 …… Substrate 13 …… Recording layer

Claims (1)

(57) [Claims] In an information recording medium having a recording layer in which an atomic arrangement is changed by irradiation of a light beam, the average composition of the recording layer is (Ge _x Sb _100-x ) _a Ch _b M _c , where Ch is Se, Te,
Chalcogen element selected from S, M is a metal selected from Pd and Au, 50 atomic% ≦ a <100 atomic%,
0 atomic% ≦ b <50 atomic%, 0 atomic% c <30 atomic%, 10
Atomic% ≦ x <80 atomic%. By irradiating a short intense pulse light and heating and quenching, it becomes an amorphous state and information is recorded. By irradiating a long weak pulse light and heating and slow cooling In the crystalline state, the recorded information is erased, and the general formula ((Te _x Sb _1-x ) _1-y Ge _y ) _1-z M
_z (M is Au, Pd, Ni, Pt, Cu, Ag, Co, Pb and Bi
Represents at least one element selected from among x, y,
And z are respectively 0.3 ≦ x ≦ 0.9, 0 <y ≦ 0.2, 0 <
wherein the composition satisfies the relationship of z ≦ 0.2).